Groutable rock bolt assembly and procedure



Feb. 15, 1966 c. I. WILLIAMS GROUTABLE ROCK BOLT ASSEMBLY AND PROCEDURE 2 Sheets-Sheet 1 Filed July 5, 1962 I. WILLIAMS CHESTE R Inventor Feb. 15, 1966 c. l. WILLIAMS GROUTABLE ROCK BOLT ASSEMBLY AND PROCEDURE 2 Sheets-Sheet :2

Filed July 5, 1962 FIG.?

C H ESTE R Atty.

United States Patent O 3,234,742 GROUTABLE ROCK BOLT ASSEMBLY AND PROCEDURE Chester I. Williams, 347 Greeubriar SE., Grand Rapids, Mich. Filed July 5, 1962, Ser. No. 207,488 2 Claims. (CI. 61-45) This invention relates to rock bolts normally engaging a hole in a rock formation to secure the formation in position. The invention concerns an assembly of components at the point where the bolt emerges from the surface, and a procedure for using this assembly to reinforce a rookformation. Groutable rook bolts normally include a temporary anchoring device used to maintain the bolt in position against the pressure of the injected grout. Grout is a cementitious material injected in liquid form, and a conduit is normally provided which will conduct the grout from the surface to the innermost extremity of the bore in which the rock bolt is positioned. A vent tube is provided for the discharge of air as the grout fills the cavity surrounding the rock bolt. This vent tube will usually be a short piece of tubing entering the rock bore alongside the bolt at the surface. In some installations (as in overhead installations), the flow of grout is reversed, so that it is admitted near the surface, with the air being exhausted from the inner extremity of the bore. The latter arrangement is also utilized by the present invention to provide a reinforcement to the communicating areas of a seamed rock formation by injecting these with grout. In the preferred rock bolt assembly, the bolt itself is a tubular rod that performs the function of a conduit extending to the inner portion of the rock bore.

The installation of the rock bolt normally involves a rotation of the bolt to set the anchor device, and the surface tube will normally be installed after this operation has taken place. Additionally, a seal is preferably applied to close off the end of the rock bore at the surface so that the necessary grout pressure can be developed. A problem in this connection has been the proper installation of the surface tube so that it does not become pinched off by the conventional nut or bearing plate engaging the rock bolt at the surface. The arrangement for the mounting and protection of the vent tube is the primary feature of this invention. In the accompanying drawings illustrating the invention,

FIGURE 1 is a sectional elevation showing the installation of a rock bolt in a bore in a rock formation, ready for grouting.

FIGURE 2 is a plan view of a bearing plate.

FIGURE 3 is a plan view of the spacing ring.

FIGURE 4 presents a side elevation of the spacing ring.

FIGURE 5 presents an end view of the clip retaining the vent tube.

FIGURE 6 illustrates a portion of the assembly shown in FIGURE 1 after the completion of a grouting operation.

FIGURE 7 is a section on the plane 77 of FIG- URE 6.

Referring to the drawings, a rock formation is indicated generally at 10, and a bore 11 has been drilled into it with standard techniques that form no part of the present invention. A rock bolt assembly generally indicated at 12 is positioned in the bore 11, and the anchor device 13 has been set by rotation of the rod 14 so that it is in solid engagement with the walls of the bore 11. The anchor device 13 may be one of several types, but the preferred form is one of the devices shown, described, and claimed in my United States application for patent Serial Number 207,530 filed on July 5, 1962.

Patented Feb. 15, 1966 The anchor 13 includes a cone expander 13a in threaded engagement with the rod 14, and also includes a C-shaped expansion shell 13!), a thrust member 13c normally fixed with respect to the rod 14, and one or more lubricated slip rings 13d axially interposed between the thrust member and the expansion shell. The rod 14 is of conventional hollow construction so that it forms a conduit leading into the inner extremity of the bore 11. The rod also has a threaded end 15 engaged by a nut 16, and a spacing ring 17 establishes a spaced relationship between the nut 16 and a bearing plate 18. A plastic composition indicated at 19 is preferably inserted around the rod 14 after the anchor device 13 has been set, and after the surface tube 20 has been secured to the rod 14 with the clip 21. The clip is illustrated in FIGURE 5, and has the opposite resilient arms 22 and 23 embracing the rod 14, with the bight 24 engaging the tube 20. The clip may be moved axially into position along the rod 14, and thus installed after the rotation of the rod 14 has been completed. It is quite likely that there may not be suflicient lateral space at the entrance of the bore 11 to accommodate the engagement of the clip 21 from a lateral direction.

The opening 25 in the bearing plate 18 receives the rod 14 in the major portion 26 of the opening, and receives the tube 20 in the minor portion 27. This keyhole-shaped opening establishes a position for the emergence of the tube 20 so that it will not be interfered with by the spacer ring 17 or the nut 16. The ring 17 may be beveled as shown in FIGURE 4 to accommodate an angular relationship between the axis of the bore 11 and the surface 27 of the rock formation. When the assembly has been arranged as shown in FIGURE 1, the grout may be pumped in at the end 28 of the tubular rod 14, and permitted to fill the bore 11 in the rock formation around the rod 14. Air will emerge through the tube 20, and a point will eventually be reached in which the grout 29 will itself emerge from the tube 20. At this time, it is preferable that both the tube 20 and the rod 14 be closed off so that the pressure of the grout within the bore may be maintained. Applicant has found that a very convenient method of accomplishing this closure is the application of pegs in the form of conventional golf tees at 30 and 31. These are left in place at least until the grout has had a chance to set. On the hardening of the grout, a very secure bond will have been created between the roughened periphery of the conventional rod 14 and the surfaces of the bore 11. The tensile strength of the rod will be applied to hold the rock formation in place so that portions of it do not break away near the surface 27.

The bolt assembly described above may be utilized in the practice of a procedure for reinforcing a seamed rock formation with grout. The seams communicating with the bore 11 may be filled by using the rod 14 as a conduit. The preferred procedure for accomplishing this utilizes the surface tube 20 as the grout inlet. Grout is pumped in until the bore 11 is at least partially full, as determined either by control of the quantity of grout, or by the emergence of grout from the hollow rod 14. In the latter case, the tube should be plunged out before the grout sets so that it may function as a conduit to the inner extremity of the bore 11. The grout surrounding the rod 14 is then permitted to set. The rod 14 is now prepared to function as a conduit, and grout may be pumped in through it to fill the interstices and seams in the formation. A grout pressure of 30 to pounds per square inch is commonly used, and the presence of the rock bolt will tend to hold the rock formation in place against the tremendous forces generated by the application of such pressures over large areas. The seal provided by the initial set grout injection will also help to prevent local migration of grout to the surface during the latter injection.

It is common to use rods 14 in lengths of five to fifteen feet in grouted installations; and Where the secondary injection procedure described above is used, the inside diameter of the rod 14 should be approximately W for a 1%" rod, and for a 1%" rod. High-tensile steel is recommended, as the required strength may be developed with less weight of material.

It is also recommended that the anchor devices 13 be encased in polyethylene bags, or covered with some similar material, and the rods 14 wrapped in paper tubes, prior to installation to prevent entrance of grit and preserve the threads in free-running condition.

The particular embodiments of the present invention which have been illustrated and discussed herein are for illustrative purposes only and are not to be considered as a limitation upon the scope of the appended claims. In these claims, it is my intent to claim the entire invention disclosed herein, except as I am limited by the prior art.

I claim:

1. A groutable rock bolt assembly, comprising:

a rod, said rod having a threaded end normally protruding beyond the surface of a rock formation engaged by said rod;

a vent tube disposed beside the said threaded end;

means normally secured said vent tube with respect to said rod;

a bearing plate containing an opening receiving said rod and a slot communicating with said opening, narrower than the outer dimension of said rod and receiving said vent tube in close adjacency to said rod;

a nut normally engaging said threaded end; and

a spacing ring normally engaging said rod and interposed between said nut and said bearing plate, said slot extending beyond the periphery of said spacing ring a distance exceeding the diameter of said vent tube.

2. A groutable rock bolt assembly, comprising:

a hollow' rod including anchor means, said rod having a threaded end normally protruding beyond the surface of a rock formation engaged by said rod; a vent tube disposed beside the said threaded end;

clip means normally securing said vent tube with respect to said rod,

said clip means embracing said tube and being movable axially with respect to said rod;

rod; a nut normally engaging said threaded end; and

a spacing ring normally engaging said rod and interposed between said nut and said bearing plate, said slot extending beyond the periphery of said spacing ring a distance exceeding the diameter of said vent tube.

References Cited by the Examiner UNITED STATES PATENTS 1,327,268 1/1920 Christians 6l36 2,233,872 3/1941 Proctor 6136 2,667,037 1/1954 Thomas 6145 2,682,152 6/1954 Bierer 6145 2,930,199 3/1960 Jarund 61-45 2,952,129 9/1960 Dempsey 61-45 FOREIGN PATENTS 1,156,187 12/1957 France. 1,222,640 1/ 1960 France.

924,624 3/ 1955 Germany. 790,483 2/1958 Great Britain. r 831,740 3/1960 Great Britain. 84,937 1/1955 Norway. 84,938 1/ 1955 Norway.

CHARLES E. OCONNELL, Primary Examiner.

40 JACOB L. NACKENOFF, EARL J. WITMER,

Examiners. 

1. A GROUNTABLE ROCK BOLT ASSEMBLY, COMPRISING: A ROD, SAID ROD HAVING A THREADED END NORMALLY PROTRUDING BEYOND THE SURFACE OF A ROCK FORMATION ENGAGED BY SAID ROD; A VENT TUBE DISPOSED BESIDE THE SAID THREADED END; MEANS NORMALLY SECURED SAID VENT TUBE WITH RESPECT TO SAID ROD; A BEARING PLATE CONTAINING AN OPENING RECEIVING SAID ROD AND A SLOT COMMUNICATING WITH SAID OPENING, NARROWER THAN THE OUTER DIMENSION OF SAID ROD AND RECEIVING SAID VENT TUBE IN CLOSE ADJACENCY TO SAID ROD; A NUT NORMALLY ENGAGING SAID THREADED END; AND A SPACING RING NORMALLY ENGAGING SAID ROD AND INTERPOSED BETWEEN SAID NUT AND SAID BEARING PLATE, SAID SLOT EXTENDING BEYOND THE PERIPHERY OF SAID SPACING RING A DISTANCE EXCEEDING THE DIAMETER OF SAID VENT TUBE. 